1. Field of the Invention
This invention relates to circular knitting machines, and in particular circular knitting machines for producing sports hosiery.
It defines the movement of the needles to form floated pattern knitting with pattern inserts of different yarns, for example of different colour, and a transparent yarn which is worked with all the needles.
2. Description of the Related Art
In general, circular knitting machines consist essentially of one or more rotating cylinders with tricks in their outer cylindrical surface. The tricks represent the guides for the needles, which during their vertical travel form the stitch loops in cooperation with the sinkers.
The basic knitting formation procedure will be described with reference to FIG. 1.
The cylinder is indicated by 1 and a trick by 2. The number of tricks is equal to the number of needles 3, which slide in their interior with vertical reciprocating motion.
Generally for sports hosiery the number of tricks and needles is between 60 and 120 per cylinder.
The needles 3 operate with reciprocating movement between a position of maximum travel and a position of minimum travel, intermediate levels also being possible.
The cylinder is rotated and with it there rotate the needles which during their reciprocating movement are fed with yarn in fixed angular positions when in their highest point of travel by yarn feed stations which present the needles with that yarn which is to be knitted in that determined knitting course and in that position.
When the needle is raised to its maximum level to receive the new feed yarn, that yarn loop which is retained in its hook opens the needle latch and moves onto its shaft, so that the loop is cleared from the needle as soon as the needle falls to a lower level. To produce hosiery articles generally only part of the available needles are used at the same time and in the same manner, except for the plain knitwork parts, for which all the needles are operated between their maximum and minimum level, all being fed with yarn at each knitting course and all being moved in the same manner.
When the machine is not producing plain knitwork, in order to produce other types of knitwork some needles are required to produce stitch loops while others have to be raised to an intermediate level to take up yarn without clearing the previous stitch in order to form a tuck stitch. Others have to be inactivated by the needle selection members and kept low, i.e. excluded from operation. Finally, others have to form the floated pattern by being raised to take up the yarn and then lowered to just a slightly lower level and then kept at this level without undergoing travel, i.e. without forming stitch loops with said yarn, until the angular position is reached in which they are required to produce stitch loops to form the floated pattern.
The needles are activated or inactivated by a series of lifting cams 4 and lowering cams 5 which act on the jacks 6 located below the needles, and in particular on their lower butt 7 and upper butt 8 respectively whenever the needle raising cams identified hereafter as 21 are extracted from their working position. If a jack 6 remains low and is not engaged by the lifting cams its needle does not participate in the stitch formation cycle until its jack raises it.
When the jacks have moved the needle into its working position, they separate from the needle butt 9 and return downwards by the effect of a lowering cam 5.
When the needle has completed its yarn take-up function and has formed its stitch loop and is therefore at its minimum level, if it does not have to take up new yarn at the next feed it remains at this level because its control jack is in its rest position and does not raise it, provided the needle raising cams are extracted. The jack is selected in the known art by members which displace it radially, for example by making contact with one of the intermediate pattern butts 10, so that it either engages or does not engage the profile of its lifting cam, the selection being done either mechanically or electromagnetically by one of a large number of methods.
With traditional mechanical selection, a certain number of butts 10 are removed from each jack, to leave only one or two which are intended to make contact with the selectors located at their level and to inactivate that jack the butts of which interfere with them.